The present invention relates to an improved method of exposing a light-sensitive layer employed for the production of reproductions of black-and-white or color patterns, in that the image of the pattern projected upon a support is taken or scanned by means of an electronic camera and stored on a recording carrier, and the light-sensitive layer is initially purely optically exposed with the image of the pattern. The invention also relates to an improved apparatus for the performance of the method which is of the type incorporating a support table for the light-sensitive layer and a purely optical projection device for the projection of the pattern at the support table, a first device with an electronic camera for producing video signals from the pattern projected at the support table and a video recording device for recording the video signals on a recording carrier.
During reproduction techniques for the fabrication of printing forms, a light-sensitive layer, preferably applied to a film is exposed as is known with the image of the pattern in order to thus produce a printing form. During the exposure or illumination of the light-sensitive layer, it is possible in particular to overcome general errors for color reproductions, which for instance could arise through the color selection for printing, or also contrast errors through the use of so-called masking techniques. The known masking techniques operate in a subtractive manner in that -- starting from colored patterns, whether such be photographic slides or direct visual patterns -- there is initially fabricated a color film negative through the use of certain color filters and then after developing the same such is placed upon the pattern. By virtue of these measures there automatically is increased the opaqueness of the patterns by a factor of 10 to 20. To compensate such effect there is required a greater quantity of light for this reproduction technique. During the projection of such patterns which are coated with a number of color film negatives, so-called sandwich patterns, at the light-sensitive layer by means of optical devices there occur difffusion disturbance effects leading to impairment of contrast, wherein for instance there must be taken into account flattening of the photographic sound recording values in contrast to the patterns.
Furthermore, such type correction masks are indifferent, in other words, when it is desired to change the mode of operation of the mask during the reproduction technique, then it is necessary to produce new color film negatives, requiring an additional expenditure in work, so that the fabrication procedures are considerably delayed.
If printing forms of colored patterns are to be fabricated for roller offset printing, then it is furthermore necessary to produce additional correction masks for secondary color separation.